Law of reflection

optics

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Reflection of light in a mirror

According to the law of reflection, images are reflected from a smooth surface, such as a mirror, at the same angle (θ2) as the incidence angle (θ1). When the eye “sees” an object in three-dimensional space in a mirror, it is actually viewing an image along sight lines created by the reflection of light from the surface of the mirror.

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calculus of variations

…of Alexandria noticed that the law of reflection—angle of incidence equals angle of reflection—could be restated by saying that reflected light takes the shortest path—or the shortest time, assuming it has finite speed. About 1660 Pierre de Fermat generalized this idea to a least-time principle for all light rays (reintroducing…

deduced from Fermat’s principle

The laws of reflection and refraction may be deduced from this principle if it is assumed as Fermat did, correctly, that in a medium of refractive index μ light travels more slowly than in free space by a factor μ. Strictly, the time taken along a…

light waves and optical systems

…polished surface, the angle of reflection between ray and normal (the line at right angles to the surface) is exactly equal to the angle of incidence. It can be seen that a convex mirror forms a virtual image of a distant object, whereas a concave mirror forms a real image.…